Telephone system



Aug. 19,1941. 5. s. MCANDREW Em 2,252 851 TELEPHONE SYSTEM Filed March 27, 1939 2 Sheets-Sheet 2' .nruhr IN VEN TORS. SMART SAMPSON MC ANDRE W CLEMENTE M/GL 04550 A rr o/wvs Y.

Patented Aug. 19, 1941 2,252,857 TELEPHONE SYSTEM Smart Sampson McAndrew andClemente Migliasso, Milan, Italy, assignors to Associated Electric Laboratories Inc.

tion of Delaware Chicago, Ill., a corpora- Application March 27, 1939, Serial No. 264,288 In Great Britain March 29, 1938 15 Claims. (C

main exchange calls \being completed with the help of an operator. The chief object of the invention is to provide particularly speedy service in a system of this type and to reduce to a minimum the attention required by the operator.

According to one feature of the invention in a telephone system including a private automatic exchange having main exchange calls completed with the help of an operator, a main exchange trunk terminates in a plug the insertion of which into the jack of a subscriber desiring an outgoing main exchange call causes ringing current to be applied automatically to his line.

According to another feature of the invention in a telephone system including a private automatic. exchange having main exchange calls completed with the help of an operator, if a subscriber is engaged in -a local call when a main exchange call is received for him the insertion into a jack associated with his line of a plug terminating the main exchange line serves to effect ringing as soon as he terminates his local call.

A further feature of the invention is that in a telephone system including a private automatic exchange having main exchange calls completed with the help of an operator, when a subscriber replaces his receiver after a main exchange call he remains connected to the exchange line for a short interval during which he is enabled to set up a further main exchange call without requiring the services of an operator.

The invention will be better understood from the following description of one method of carrying it into effect which should be taken in conjunction with the accompanying drawings comprising Figs. 1 and 2. Fig. 1 shows the equipment of a cord circuit associated with a main exchange line, while Fig. 2 shows the operators equipment, a typical subscribers line circuit and the equipment associated with an information trunk.

Each subscribers line is connected tola jack with a special trunk offering plug whereby she may communicate-with busy lines. The various types of call which can be set up with the aid of the equipment will now be considered in turn. 7

For a local call the subscriber whose line i, 2 is shown in the lower part. of Fig. 2 removes his receiver whereupon relay Q operates over the line in series with the relay LR which is not however operated at this time. Relay Q locks up at armature 9, switches the line through to the normal line circuit at armatures I and 8 whereupon a finder switch is set in operation in the usual manner, and at armature 10 lights the busy lamp BL at the operators position. The call is then completed over the local equipment by dialling in the usual manner.

If the subscriber wishes to set up an outgoing main exchange call, he presses a button on his instrument before removing his receiver. This has the efiect of earthing the line so that relay Q is short-circuited and prevented from operating while relay LR now receives sufficient currentto energize it. It thereupon locks up at armature H, at armature l2 lights the calling lamp CL, and at armature l3 applies earth to lead l4 extending to the connector bank so as to busy the line to local calls. The operator on noting the lighted condition of the lamp CL inserts the plug of a free exchange line, for instance plug Pl, into the jack J l associated with the calling party. Thereupon relays G and C0 operate in series over the sleeve and the latter at armatures l6 and I1 disconnects the line from thelocal equipmenh at armature l8 releases relay LR, and at armature l9 applies a further earth to the lead l4. Relay G at armature 26 lights the supervisory lamp SL, at armature 21 completes a start circuit for the ringing generator GN and at armatures 25 and 28 connects this generator to the calling line in series with the ring trip relay F so that the subscribers bell rings.

When he lifts his receiver, relay F operates in the usual manner and at armature 3| locks up over its lower Winding, at armature 29 extinguishes the lamp SL, at armature 32 completes a circuit for relay P, at armature 33 interrupts the generator start circuit and at armatures and 34 disconnects the ringing and connects the subscriber through to the main exchange trunk. His loop is thereupon. extended to relays A and M whereupon relay A operates but relay M does not as it is difierentially wound. Relay A at armature 44 energizes relay B and at armature 45 completes a loop across the junction to the main exchange including the retard R. Relay B completes points in the speaking circuit at armatures 40 and 43 and at armature 42 opens the circuit of relay P so that this relay is ineffective at this time.

The subscriber may'now proceed to set up the main exchange connection by dialling. During each train of impulses relay C is operated over armatures 44 and 4! and at armature 4g short-circuits the retard R and thus gives an im pedance-free loop. a

At the end of the conversation when the sub: scriber replaces his receiver, relay A releases followed by relay B and .the loop to the main exchange is opened thereby releasing the equipment thereat. The release of relay B again completes a circuit for the pendulum relay P which thereupon vibrates its armature 20 so as armature I06 opens the initial energising circuit of relay H so as to prevent the association of any further cord circuits with the operators equipment in case two keys should inadvertently be operated at the same time. Relay H locks up over armature 53, at armature 54 prepares a circuit for relay J and at armatures and 55, connects the trunk line through to the operators (handset which is assumed to be inserted in the to complete a circuit intermittentlyfor relay' N. i This relay is made slow to energize and the arrangement is such that it is .not operated for several seconds. If the subscriber wishes to set up another main exchange call immediately, he

may doso as soonas the previous call his been u cleared. and, provided he removes his receiver again before the pendulum relay P has been effective to operate relay N, no signal is given to the operator. As soon as relay B again operates, the circuit of the pendulum relay P I isfl'openedand thus there is no further'circuit for operating relay N. I

In the more usual case in which the subscriber does not wish to. make a furtherexohange call,

at armature 2| completes a circuit by way of the interrupter H to flash. the supervisory lamp SL.

At armaturesZZ and 23 the operation of common visual and audible alarms is initiated whileat the flashing 'ofthe supervisory lamp withdraws the plug Pl from the jack J l whereupon relays P and N release and all the cord circuit equipment is restored to normal. If the subscriber should wish to attract the attention of the operator he can do this byioperating' his push button which will produce the effects already described including. the lighting of the lamp CL.

Consideration will now be given to the handling 'of 'an incoming call from the'main exchange.

When such a call is received, relay E is operated by ringing currentand thereupon at armature 48 looks up by way of its lower winding to earth at armature 42; Relay E also at armature 12 lights the trunk calling larnp TL and at armature 41 opens its own initial energising circuit.

The operator on noting the lightingof the lamp TL. replies by throwing the speaking key SK,

thereupon at spring 13 releas ng relay E and operating relay D, at spring 14 preparing a circuit for relay Cl, at spring 15 completing a ciruit for relay. I- I, and at spring '16 preparing a locking circuit for relay 1-1 over its lower winding.

Relay. operates in serieswith the lower winding o'f relay and at armatures U4 and H disconnects the toll offering plug P2 and at l relay N will eventually operate and thereupon operation ensues.

jack J2. v

The operator will now ascertain the requirements of the calling party and insert the plug Pl. into the jack of the wanted party, for instance the jack J l. Thereupon relays G and CO operate in series and the wanted line is rung as previously described. The operation of relay D lights the supervisory lamp at armature 35, and also at armature 31 it looks over the release key RK and at armature 38 completes a loop across the main exchange line. Consequently the operator may withdraw from the connection before the wanted party replies without giving any'false supervisory signals. This she does by restoring the speaking key SK whereupon relays H and DI release leaving the operator free to attend to other calls.

If the operator should wish to talk to the called party without being audible to the calling party, she may operate the splitting key PK, Fig. 2, which has the effect of energising relay J. This relay at armatures El and 62 closes a loop including the operators dial DS across the main exchange line while leaving the operators headset connected to the local subscribers side of the circuit. When the wanted party replies, relay F is energised and extinguishes the supervisory lamp and relays A and B are then operated and relay B at armature 42 releases relay D. 1f the wanted party does not reply, the operator will inform the calling party accordingly after operating the key SK if she had previously withdrawn. She then restores key SK, momentarily operates key RK to release relay D and removes the plug whereupon all the equipmentwill be restored to normal as previously described.

If the wanted party is busy, the operator may plug into his jack and in this case he will be rung as soon as he is free. Since he is already engaged in a local call his relay Q will be operated and at armature l0 will have removed the short-circuit from the resistance I61 in the sleeve circuit. This prevents the operation of relay'G. and hence the application of ringing current. As soon as relay Q de-energizes how- .ever on the termination of the local call, resistance I6! is again short-circuited and relay G then operates to produce the effects previously described.

'for relay Bl which thereupon at armature lfll short-circuits itself so that a self-interrupting The adjustment of the relay is such that this produces a tone and since armature I02 will vibrate similarly this tone will be applied to the line by way of the tertiary winding, of the induction coil IC. The operator then advises the subscriber that there is a long distance call awaiting him and when he hangs up, the normal plug associated with the exchange line is employed for completing the call. The tone circuit also comes into action if the operatorcuts in on an existing call since relay Cl is then operated from earth at armature 44.

On any main exchange call, whether incoming or outgoing, it is possible for the subscriber to switch to the local equipment and set up an enquiry call while holding the main exchange call. This is effected bythe operation of the push button which unbalances the line and energises relay M, relay A remaining held, Relay M at armature 46 completes a circuit for the two-step relay K which first operates armature 64 so as to short-circuitits upper winding. When the button is released, relay M de-energises and relay K then, energises fully over its two windings in series and at armature 62 prepares a circuit for flashing the supervisory lamp, at armature 65 closes a loop across the main exchange line to, hold the connection, at armature fifitransfers the control circuit from relay M to relay L, at

armature 6'I initiates the operation of the visual alarm circuit, and at armatures 63 and 68 switches the speaking leads to the local equipment by way of leads 80 and 8|. The subscriber may then set up a local number by dialling in the usual way., In order to reconnect himself to the main exchange line he again operates his push button whereupon due to the energisation ofrelay M earthfrom armature 46 is extended over armature BBto energise relay L.

Thereupon at armature 69 relay. K also is made dependent on the earth from armature 4B and at armature 10 a further loop is closedacross the line. When the push button is released, relays K and L both de-energise and the subscriber is "relay B is now de-energised while relay K is energised, the trunk supervisory lamp TL is flashed over armatures 62 and 39. Theoperator then comes in on the line by throwing the speaking key. SK and on ascertaining the wishes of the main exchange partytransfers the plug to the appropriate line. When the original subscriber replaced his receiver, the previouslymentioned circuit for relay Pwas completed so that after the predetermined time. interval this subscribers relay C de-energises and he is able to make a local call even if .the operator has not yet replied. I

;' Itwill be seen thaton-an incoming call when a locking circuit is completedjfor relay Ea circuit is also completed for the thermostat T.

Consequently if the call is not answered within the time limit of the thermostat, contacts 59 are closed to energise relay B. This relay at armature. 42opens the locking circuit ofrelay E which thereupon de-energises and also the circuit 01? the thermostat which commences to cool.

When contacts 50 open, relay B is de-ene'rgised and all the equipment is restored to normal.

The attendants cabinet is provided with an information trunk to which access is obtained over the local equipment by dialling a particular number. This results in connection being made to leads I and I2l and ringing current applied thereover operates relay AZ. This relay at arinature I2 2 lights the lamp IL and locks up over its 1 lower winding. The operator replies by throwing the key IK whereupon at contacts I23 and I24 relay A2 is tie-energised and the lamp IL extinguished, While at contacts I25 and I26 circuits are prepared for relay B2. This energisesover its upper winding from earth at armature 1G6 and locks up over its lower winding in series with relay DI which performs the functions previously described. Relay B2 at armatures I21 and I28 connects the incoming trunk through to the operators headset and she may then supply the desired information.

It may happen that the operator wishes to speak to a local party who is not entitled to main exchange service and whose line does not therefore appear in the jack field. I This may be done over the information trunk which is seized by operating key IK whereupon relay B2 energises. When the operator moves her dial switch DS on. normal a circuit is completed for relay G2 which atarmatures I31 and I32 connects the information trunkto the dial impulse springs so that a connection may be set up over the local'equipment.

The operator may also dial the main exchange equipment and it will be seen that if key SK is operated, the movement of the dial off-normal.

will have the effect of energising relay J. I

The rectifiers RC connected back to back across the operators receiver are for the purpose of reducing clicks, i

l We claim:

'1. In atelephone system, a plurality of subscribers lines, a linizcircuit common to said lines,

means for connecting saidlink circuit to a calling one of. said lines to permit the extension over said link of the desired call, and means responslve to said connection of the link to the calling 3;In a telephone system wherein each of a plurality of substations normally has a ringer 'c'onn'ected to its respective line, and wherein a subscriber at any of said'substationsmay initiate a call without disconnecting-the ringer at that station, a link circuit comm-on tosaid substa- I tion, meansforconnecting said link to the line *of a calling substation to permit the extension 0f the desired call ove'r said' link, and means responsive to said connectionof the link to the line of the calling substation for automatically applyingringing current to that. line to operate the ringerat said calling substation. I4. Inl a telephone'system' wherein two ex- -cl1'anges are connected by. an inter-exchange trunkxline,"subscribers lines terminating: at one ot the exchanges, means in said one exchange for connecting :a calling subscribers line to said trunk line to enable that subscriber to make an outgoing call, and means responsive to said connecting of the calling line to the trunk line for automatically applying ringing current to said calling line.

5. In a telephone system wherein two exchanges are connected by an inter-exchange trunk line, subscribers lines terminating at one of the exchanges, means in said one exchange operated at times to connect said trunk line to a calling subscribers line to enable that subscriber to make an outgoing call and operated at other times. to connect said trunk line to a called subscribers line to permit an incoming call to be extended thereto, means responsive to either such connection of said trunk line to a subscribers line for automatically applying signalling current to that subscribers line, said current being of the same character whether said subscribers line is a calling or a called line.

6. In a telephone system, a local exchange, subscribers" lines terminating at said exchange, means in the exchange for completing local connections between said lines, an operators position having a jack for each of said lines, a trunk line incoming to said position from another exchange, a plug for said trunk line at times inserted manually by the operator at said position into the jack for oneof said subscribers lines while that line is engaged in a, local connection, and means at said position thereafter responsive to the release of said local connection for transmitting; ringing current over said one subscribers line.

'7. In a telephone system, subscribers lines each having a jack, means for making said linesbusy when same are engaged in calls, a link circuit including a plug adapted to be inserted in the jacks of wanted subscribers lines, means in said link circuit normally effective responsive to such insertion of said plug, a wanted subscriber's line to transmit ringing current over that line, said first means rendering said last means inefiective if the wanted line is engaged in another call and said last means then responsive to the wanted line becoming idle after said connection of the terminal therewith to transmit the ringing, current over said wanted line.

8. In a telephone system, a calling line and a busy wanted line, a jack for said busy wanted line, a plug inserted into said jack while said wanted line is busy to prepare a connection thereto from said calling line, and means responsive to the wanted line thereafter becoming idle for transmitting ringing current over said wanted line.

9. In a telephone exchange, an operator's position, subscribers lines appearing at said position, a trunk line incoming to said position from another exchange, means including 'a plug and jack at said position operated at times to connect a calling one of said subscribers lines to said trunk line to permit the extension of an outgoing call, a slow to operate relay, means operated over said calling line after the call is extended, means controlled by said last means thereupon to commence transmission of impulses to said slow relay to operate same after an interval, said relay eflective upon operation to disconnect said calling line from said trunk line, said second means attimes operated over said calling line during said interval to initiate another cell andefiective at such times to. prevent said operation of said relay, thereby to permit the extension of said other call over said trunk line before the disconnection of same from said calling line.

10. A telephone exchange as claimed in claim 9, having a disconnect signal at said operators position opera-ted by said last means only if said other call is not initiated during said interval.

11. A telephone exchange as claimed in claim 9, and having automaticswitches normally accessible to said subscribers lines for the extens-ion of local calls, means for blocking said calling lines access to said switches during said outgoing call, and means controlled by the means operated to terminate said outgoing call for unblocking said calling lines access to said switches after said interval.

12. In a telephone system wherein calls are extended over automatic switching equipment, subscribers lines, 'a link circuit having access to said switching equipment, means operated at times to connect a calling one of said lines, to said link circuit to permit the extension of a call over said automatic switching equipment, means, operated over the calling line after a call is extended to transmit 'a release signal to said switching equipment, timing means normally controlled by said last means to automatically disconnect said calling line from said link circuit a predetermined interval of time after said transmission of the release signal, said interval being of not less than two seconds duration, said second means at times controlled during said. interval by said calling subscriber to initiate another call and effective at such times to render said timing means ineffective to disconnect said link from the line, thereby to enable said other call to be extended over said link before disconnection of same from said calling, line.

13. In a telephone system, a subscribers line, two paths individual to said lineover which con nections may be extended'from said line, means for completing a connection over one of said paths thereby to extend a call from said line, means operated over said line by the subscriber when he desires to terminate said call, timing means associated with said connection thereupon rendered operative by said last means, means normally controlled by said timing means tolrelease said connection after an interval, said sec-- ond means responsive to an operation by 'said subscriber during said interval to prevent said last means from releasing said connection at the end, of said interval, and means responsive to the same operation by said subscriber after the end of said interval to initiate a call over the other of said paths.

14. In a telephone system wherein automatic switches may be controlled by calling subscribers to extend desired connections, an operators po- 7 sition, subscribers lines each having an individual jack at said position and each having access to said switches over an individual path independent of said position, a link circuit at said position having a plug adapted-to be inserted into the jack of any of said lines to complete a connection thereto from said link,means in saidlink operable over a line when said plug is inserted into the jack of that line, timing means rendered operative responsive to an operation of said last means, means normally controlled'by said timing means then to release the connection to said line afteran interval of time, said first meansresponsive to an operation by the subscriber during said interval toprevent said last means from releasing said connection at the end of said interval, and means responsive to the same operation by said subscriber after the end. of said interval to initiate a call over the individual path for said line even if said plug is still in the jack for that line.

15. In a telephone system wherein automatic switches may be controlled by calling subscribers to extend desired connections, an operators position, subscribers lines each having an individual jack at said position and each having access to said switches over an individual path independent of said position, a link circuit at said position having a plug adapted to be inserted into the jack of any of said lines to complete a connection thereto from said link, and

means controlled over a calling one of said lines for at times seizing a switch over said path while said plug is in the jack for said calling line.

SMART SALMPSO'N' MCANDREW. CLEMENTE MIGLIASSO. 

